The present invention relates generally to remote alarm reporting systems, and in particular, to a supervised alarm reporting system which is capable of providing enhanced security.
A variety of security systems have been developed to satisfy the ever-increasing need for the remote monitoring of various premises, including both business and home applications. Generally, this is accomplished by providing the premises with a local terminal, or reporting unit, which is capable of receiving signals from various sensors placed throughout the premises, interpreting such signals, and interacting with a central office or station to advise the central facility of potential alarm conditions. The sensors communicating with the local terminal may be used to provide any of a variety of functions, including smoke and fire detection, the detection of intruders (i.e., possible break-ins), or to monitor local conditions such as temperature, pressure or other desired parameters. The corresponding central facility might constitute any of a number of private companies which have been established for security or other monitoring purposes. The key to the effectiveness and integrity of the system provided often depends upon the means which are used to establish communications between the local terminal provided at the premises and the monitoring equipment provided at the central facility. A number of systems have therefore been devised to provide such communications.
Perhaps the most common means of communication between the local terminal and the central facility is the switched network telephone lines which connect these two locations. The local terminal provided at the remote premises is connected to the switched telephone line network associated with the premises, to establish remote communications. Often, such communications are initiated by the local terminal, which automatically dials the central facility when a potential alarm event has been detected (one-way communications). While such communications may be accomplished by voice (a recorded message), the current trend is for such communications to be accomplished through digital communicators, which are capable of providing more detailed information regarding the potential alarm condition. Communications via the switched telephone line network are popular because they are inexpensive, well proven and reliable. Moreover, the switched telephone line network is already in place, readily accessible, and serviced by a third party. A cost effective security system results.
However, such systems provide only limited security because of the free accessibility of others to the switched network telephone lines. The lines are not secured, and may be cut either accidentally, or intentionally, severing the link between the local terminal and the central facility. In fact, periodic interruptions are generally necessitated by the testing requirements which are imposed by the utilities that install and service such telephone lines. Since in the case of one-way communications the central facility has no way of knowing whether or not the communicating lines are operational, it is possible for alarm conditions signaled by the local terminal to go undetected if the telephone line is defective.
For this and other reasons, efforts were made to develop supervised communicating systems adaptable for use in connection with switched network telephone lines (two-way communications). Due to their manner of operation, such systems are capable of providing an indication as to the condition of the communicating telephone lines, as well as the local terminal. An example of such a system may be found with reference to U.S. Pat. No. 4,442,320, which describes the "Subscriber Terminal Unit" alarm reporting system of BT Telecom, Inc. Such alarm reporting systems, which are generally known as derived channel systems, modify the above described one-way system by providing means which allow the central facility to verify the integrity of the system, and the communicating telephone lines. In connection with the "Subscriber Terminal Unit" alarm reporting system, this is accomplished in two ways. First, the central facility is permitted to periodically interrogate the local terminal at the remote premises, to determine its status. In addition to indicating whether or not there are any alarm conditions, this also has the benefit of verifying that the communicating lines are intact. Second, there is additionally provided a tone, having a frequency below the audible range, which is transmitted by the local terminal at specified times. Again, in addition to the reporting function of this tone, this additionally provides a means for verifying the integrity of the communicating telephone lines.
Such derived channel systems therefore have the advantage of indicating whether or not the system is operational, and is properly reporting its condition. This avoids the potential "blackouts" inherent in one-way communicating systems, thereby serving to significantly enhance security.
However, this supervisory capability has been found to cause yet another difficulty. When, for whatever reason, the local terminal ceases to report its condition, the associated central facility is constrained to declare a break-in since it is not sure whether the cessation of operations results from an equipment failure, a test of the telephone lines by the local utility, or an actual break-in. This necessarily results in a significant number of false alarms, since equipment failures are inevitable, and since the utilities must periodically test their equipment. Such false alarms have led to a certain amount of apathy on the part of the police, and have even caused some police departments to limit the number of responses which they will make to calls received regarding a given premises.
Yet another system which is commonly used is the direct wire system. In this system, communications (either one-way or two-way) are established by a private (shared or dedicated) line running directly between the local terminal and the central monitoring facility. Since this system is no longer dependent upon the switched telephone line network, a greater degree of predictability is provided. In particular, there is no longer a need to account for third party testing of the communicating system. However, there is still presented the potential for interrupted communications to be the result of either an equipment failure, an accidental cutting of the line, or an actual break-in, again leading to the above-described problems. The central facility must again take action based upon assumed information, declaring a break-in when in fact there might be none. Moreover, any increases in security which are provided by such a system are counterbalanced by significant increases in cost, since the communicating lines of the system require special installation as well as dedicated service and maintenance.
Yet another system involves the replacement of wired lines with radio communications. While it is significantly more difficult to "cut" radio communications between the local terminal and the central facility, such jamming techniques do exist. Consequently, a one-way radio system, although more reliable than a wired one-way system, will still suffer from the disadvantage that the central facility is not made aware of whether or not the system is in operation. A two-way radio system would enable a supervisory function to be added. However, this requires continuous two-way communications by way of radio. Such systems are therefore subject to significant radio frequency capacity limitations in view of the regulatory constraints which are in place regarding the use of radio waves, and in terms of the number of frequencies which are available for use in a particular system (limiting the number of possible installations). Yet another factor to consider is the significant cost of installation and maintenance which such a system necessarily entails.
Moreover, a consideration which is common to each of the above-described systems is that, irrespective of the elegance of the system, discontinued signals from the local terminal cannot be interpreted. This generally necessitates the declaration of a break-in when in fact there may be none. Once the line of communications (wired or radio) has been cut, it is not possible for the central facility to determine the exact nature of the problem. Because of this, a significant potential exists for police to be dispatched to a particular premises for no reason. Still further complicating matters is that in connection with systems which are capable of reporting more than one type of alarm condition, it is possible for the wrong remedy to be dispatched to the premises, since the exact nature of the alarm cannot be determined. For example, the police may be dispatched to a premises when in fact the discontinued signals result from a fire, a medical emergency, or a needed repair. It is clearly unreasonable to dispatch all such remedies to a given premises every time communications with a particular premises cease.
For this reason, efforts have been made to develop dual technology systems which combine two of the above-described systems in a single unit. Generally, this is accomplished by combining a wired system and a radio system. If either unit ceases to operate, the remaining unit operates to convey information to the central facility. However, unless the wired system and the radio system are supervised, the potential still exists for many of the above described problems to arise. Ultimately, this can be remedied by providing a supervised wired system and a supervised radio system. However, while providing significant security, such a system is prohibitively expensive, and still suffers from the significant limitations imposed by the need for constant two-way radio communications.